5 March 2014 Optical monitoring of shock wave-induced spreading depolarization and concomitant hypoxemia in rat brain
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Blast-induced traumatic brain injury is a growing concern, but its underlying pathophysiology and mechanism are still unknown. Thus, study using an animal model is needed. We have been proposing the use of a laser-induced shock wave (LISW), whose energy is highly controllable and reproducible, to mimic blast-related injury. We previously observed the occurrence of spreading depolarization (SD) and prolonged hypoxemia in the rat brain exposed to an LISW. However, the relationship between these two events is unclear. In this study, we investigated the spatiotemporal characteristics of hypoxemia and SD to examine their correlation, for which multichannel fiber measurement and multispectral imaging of the diffuse reflectance were performed for the rat brain exposed to an LISW. We also quantified tissue oxygen saturation (StO2) in the hypoxemic phase, which is associated with possible neuronal cell death, based on an inverse Monte Carlo simulation. Fiber measurement showed that the region of hypoxemia was expanding from the site of LISW application to the distant region over the brain; the speed of expansion was similar to that of the propagation speed of SD. Simulation showed that oxygen saturation was decreased by ~40%. Multispectral imaging showed that after LISW application, a vasodilatation occurred for ~1 min, which was followed by a long-lasting vasoconstriction. In the phase of vasoconstriction, StO2 declined all over the field of view. These results indicate a strong correlation between SD and hypoxemia; the estimated StO2 seems to be low enough to induce neuronal cell death.
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Wataru Okuda, Wataru Okuda, Satoko Kawauchi, Satoko Kawauchi, Hiroshi Ashida, Hiroshi Ashida, Shunichi Sato, Shunichi Sato, Izumi Nishidate, Izumi Nishidate, "Optical monitoring of shock wave-induced spreading depolarization and concomitant hypoxemia in rat brain", Proc. SPIE 8928, Optical Techniques in Neurosurgery, Neurophotonics, and Optogenetics, 892829 (5 March 2014); doi: 10.1117/12.2040899; https://doi.org/10.1117/12.2040899

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